class_docstr: A lazy version of np.stack which avoids copying the memory until it is
  needed.
class_docstr_tok: ["A","lazy","version","of","np.stack","which","avoids","copying","the","memory","until","it","is","needed","."]
code: def __init__(self, history, axis=None):
      self.history = copy.copy(history)
      self.axis = axis
  
file_path: coach/rl_coach/filters/observation/observation_stacking_filter.py
imports: import copy
  from collections import deque
  import numpy
  from rl_coach.core_types import ObservationType
  from rl_coach.filters.observation.observation_filter import ObservationFilter
  from rl_coach.spaces import ObservationSpace, VectorObservationSpace
label_desc: Use image node_id 1 to create a new LazyStack object from inherited base classes: object with example: obj = LazyStack(history, axis)